selftest: fix flower terse dump tests

Iproute2 tc classifier terse dump has been accepted with modified syntax.
Update the tests accordingly.

Signed-off-by: Vlad Buslov <vlad@buslov.dev>
Fixes: e7534fd4

 ("selftests: implement flower classifier terse dump tests")
Link: https://lore.kernel.org/r/20201107111928.453534-1-vlad@buslov.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>